Homogeneous solid solution oxidizing composition

ABSTRACT

A HOMOGENEOUS SOLID SOLUTION OXIDIZING COMPOSITION WHICH IS THE RESULT OF THE ADMIXTURE OF A HYDROXYLAMMONIUM SALT AND A HYDROLYZED POLYMER OR CERTAIN OTHER POLAR POLYMER BINDER MATERIALS, E.G., POLAR POLYMERS CONTAINING POLY-HYDROXYL, POLY-AMINE, POLY-ESTER AND POLYCARBOXYL FUNCTIONALLY.

"United States Patent O1 ice 3,697,340 Patented Oct. 10, 1972 Int. Cl.C06f N04 US. Cl. 149-49 15 Claims ABSTRACT OF THE DISCLOSURE Ahomogeneous solid solution oxidizing composition which is the result ofthe admixture of a hydroxylammonium salt and a hydrolyzed polymer orcertain other polar polymer binder materials, e.g., polar polymerscontaining poly-hydroxyl, poly-amine, poly-ester and polycarboxylfunctionality.

BACKGROUND OF THE INVENTION This invention relates generally tooxidizing compositions and more particularly to a homogeneous solidsolution oxidizing composition useful for propellants and explosives.

In the past, propellant compositions which employed solid oxidizingcompositions have been of the non-homogeneous composite type wherein thecrystalline oxidizers were suspended in a resinous binder. Onesignificant disadvantage of these composite type propellants is theinfluence of the particle size of the ingredients upon the totalefiiciency of the propellant. For example, at times it is necessary touse combinations of particle sizes of an ingredient (i.e., bimodal ormultimodal distributions) in order to achieve optimum packing andprocessibility. Furthermore, changes in particle size result invariations in the available surface of ingredients and therefore affectthe rates of reaction involved. Even more important, the variation inrate of reaction affects the burning rate of the propellant, which mustbe carefully controlled in order to fulfill the mission. Obviously, allthese checks on the control of particle sizes are tedious and timeconsuming.

Recently, a new class of solid oxidizers, in the form ofhydroxylammonium salts, such as hydroxylammonium perchlorate (HAP) andhydroxylammonium nitrate (HAN) have been found to be extremely useful assuch in liquid monopropellant compositions. However, attempts to employthese hydroxylammonium salts as solid oxidizers in conventionalcomposite type propellant compositions (i.e., with conventional resinousbinder materials) have met with very little success. In addition to thegeneral disadvantages of composite type compositions as hereinbeforediscussed, several other factors may be attributed to this unsuccess.Firstly, the hydroxylammonium salts are such chemically strong oxidizingagents that they disrupt the cross-linking of these conventional bindermaterials. Secondly, because of the low melting points of thehydroxylammonium salts, the solid oxidizing compositions containing themexhibit changes in properties during their utilization which causeunstable burning and other deleterious effects. For example, when thehydroxylammonium salts are combined with conventional binders andincorporated within a rocket motor casing, the crystals of the saltoxidizer change in apparent volume at their melting point and cause thebinder material to break up and form cracks, which allow for increasedinternal pressure and eventual rupturing of the motor. Furthermore, thelow melting points of the hydroxylammonium salts completely precludetheir utilization in air-launched missiles or launching vehicles becausethe heat encountered from air friction alone causes the salts to melt.

Another problem which exists with the use of solid hydroxylammonium saltoxidizing composition is the extreme hygroscopicity of the salts.

SUMMARY OF THE INVENTION It is therefore one object of this invention toprovide new hydroxylammonium salt oxidizing compositions.

Another object of this invention is to provide a hydroxylammonium saltoxidizing composition wherein no influence of particle exists.

Still another object of this invention is to provide an oxidizingcomposition which comprises a hydroxylammonium salt in solid form butwhich does not exhibit any deleterious changes in properties at themelting point temperature of the salt.

It is a further object of this invention to provide a hydroxylammoniumsalt oxidizing composition which is substantially non-hygroscopic.

These and other objects are accomplished by providing a homogeneoussolid solution of a hydroxylammonium salt oxidizer dissolved in asuitable polymer binder material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The solid solution oxidizingcompositions of the present invention are prepared by dissolving,preferably at elevated temperatures, a melted hydroxylammonium salt suchas hydroxylammonium perchlorate (HAP), hydroxylammonium nitrate (HAN) orderivatives thereof, e.g., the N-methyl, N-ethyl, O-methyl and O-ethylderivatives, and mixtures thereof in a suitable polymer binder materialor vice versa, i.e., wherein the binder is dissolved in the oxidizersalt. Although, any polymer material that is capable of forming a solidsolution with the hereinbefore identified hydroxyl-ammonium saltoxidizers may be employed in the practice of this invention, preferablypolymers containing polyhydroxyl, poly-amine, polyester andpoly-carboxyl functionality are used. Specifically, some of these arepolyvinylalcohol, polyvinylacetate, partially hydrolyzedpolyvinylacetate, and polyvinylpyrrolidone and copolymers of thesematerials. The molecular weights of the polymers employed are notcritical but preferably are in the range of from about 20,000 to200,000.

The ratio of the materials comprising the oxidizing compositions of thepresent invention may vary within a wide range, e.g., about 30-85percent-by-weight oxidizer to 70-15 percent-by-weight binder may beused, but preferably the ratio employed is that which provides thegreatest amount of oxidizer salt to the least amount of binder polymericmaterial and the greatest efiiciency. This, of course, is dependent uponthe particular binder polymer employed and its solubility relationshipwith the particular hydroxylammonium salt employed.

The resultant oxidizing composition is a homogeneous solid solutionwherein the hydroxylammonium salt oxidizer is completely enveloped bythe polymer binder material. An alternative procedure which may be usedto prepare the solid solution oxidizing compositions of the presentinvention is to dissolve both the hydroxylammonium salt or mixturesthereof and the binder polymeric material in a common solvent, such asmethanol, ethanol, water, etc., and subsequently evaporate the solvent.

Many additives may be added to the oxidizing compositions withoutdeparting from the scope of the present invention. For example, thecompositions may be modified by the addition of (a) fuels such asaluminum,

beryllium and additional polymers, (b) plasticizers, (c) burning ratemodifiers, (d) stabilizers, and (e) small amounts of other solubleoxidizers such as lithium perchlorate, ammonium perchlorate and ammoniumnitrate. Preferably, however, the additives should not comprise morethan 50 percent by weight of the total oxidizing composition.

A preferred oxidizing composition within the scope of the presentinvention is the homogeneous solid solution of hydroxylammoniumperchlorate (HAP) in polyvinyl alcohol, modified by the addition ofaluminum.

The general nature of the invention having been set forth, the followingexamples are presented as specific illustrations thereof. It will beunderstood that the invention is not limited to these examples, but issusceptible to different modifications that will be recognized by one ofordinary skill in the art.

EXAMPLE 1 Composition percent weight HAP 81.0 Polyvinyl alcohol 19.0

The composition of Example 1 has a specific impulse of 250 seconds.

EXAMPLE 2 Composition percent weight HAN 80.0 Polyvinyl alcohol 20.0

The composition of Example 2 has a specific impulse of 236 seocnds.

EXAMPLE 3 Composition percent weight HAP 60.0 Polyvinyl alcohol 15.0Aluminum 25.0

The composition of Example 3 has a specific impulse of 262 seconds and adensity impulse of 509 seconds.

EXAMPLE 4 Composition percent weight HAN,55.0 Polyvinyl alcohol 15.0Aluminum 30.0

The composition of Example 4 has a specific impulse of 264 seconds.

EXAMPLE 5 Composition percent weight HAP 70.0 Polyvinyl alcohol 30.0

The composition of Example 5 has a burning rate of 1.35 inches/sec. at77 F. and 500 lb./sq. in. pressure and 3.9 inches/sec. at 77 F. and 2500l'b./sq. in.

Obviously numerous modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described herein.

What is claimed and desired ot be secured by Letters Patent of theUnited States is:

We claim:

1. An oxidizing composition comprising a hydroxylammonium salt and apolymeric binder material capable of forming a solid solution with saidsalt; wherein said salt is selected from the group consisting ofhydroxylammonium perchlorate, hydroxylammonium nitrate, N-methyl-hydroxylammonium perchlorate, N-ethyl-hydroxylammoniumperchlorate, N methyl-hydroxylammonium nitrate, N ethyl hydroxylammoniumnitrate, O methyl hydroxylammonium perchlorate, O-ethyl-hydroxylammoniumperchlorate, O- methyl-hydroxylammonium nitrate, O-ethylhydroxylammonium nitrate, and mixtures thereof and said polymeric'binder material is selected from the group consisting of polyhydroxylpolymers, poly-ester polymers, poly-carboxyl polymers, and poly-aminepolymers.

2. The oxidizing composition of claim 1 wherein said hydroxylammoniumsalt is selected from the group consisting of hydroxylammoniumperchlorate, hydroxylammonium nitrate, N methyl-hydroxylammoniumperchlorate, N ethyl-hydroxylammonium perchlorate, N-

methyl-hydroxylammonium nitrate and N-ethyl-hydroxylammonium nitrate andmixtures thereof.

3. The oxidizing composition of claim 1 which further includes'amaterial selected from the group consisting of fuels, plasticizers,burning rate modifiers, stabilizers and other soluble oxidizers.

4. The oxidizing composition of claim 2 wherein the hydroxylammoniumsalt is hydroxylammonium perchlorate.

5. The oxidizing composition of claim 2 wherein said hydroxylammoniumsalt is hydroxylammonium nitrate.

6. The oxidizing composition of claim 2 wherein said polyhydroxylpolymer is polyvinylalcohol.

7. The oxidizing composition of claim 2 wherein said polyamine polymeris polyvinylpyrrolidone.

8. The composition of claim 1 wherein the weight of said salt variesfrom about 30-85 percent by weight of said composition and the weight ofsaid binder material varies from about -15 percent by weight of saidcomposition.

9. The composition of claim 10 wherein the weight of said salt variesfrom about 3085 percent by weight of said composition and the weight ofsaid binder material varies from about 70-15 percent by weight of saidcomposition.

10. The composition of claim 9 comprising hydroxylammonium perchlorateas the salt and polyvinyl alcohol as the polymeric binder material.

11. The composition of claim 10 additionally containing a fuel.

12. The composition of claim 11 wherein said fuel is aluminum.

13. The composition of claim 11 wherein said fuel not comprise more than50 percent by weight of the total oxidizing composition.

14. The composition of claim 13 wherein said aluminum does not comprisemore than 50 percent by weight of the total oxidizing composition.

15. The composition of claim 9 comprising hydroxylammonium nitrate asthe salt and polyvinyl alcohol as the polymeric binder material.

References Cited UNITED STATES PATENTS 3,401,067 9/1968 Fee et al.149-60 X CARL D. QUARFORTH, Primary Examiner S. J. LECHERT JR.,Assistant Examiner US. Cl. X. R.

